(a) Field of the Invention
The present invention relates to a vacuum glass panel, and more particularly to, a plurality of spacers interposed between two glass plates to support an external force and an edge sealing technology integrally welding edges of two plates separated from each other.
(b) Description of the Related Art
A vacuum glass panel has a structure where a vacuum space is formed between two glass plates, and receives attention as future door and window materials due to its insulation performance. The vacuum glass panel receives complex dynamic stresses such as pressure applied by atmospheric pressure, a temperature difference between an inside and an outside, wind and the like. It is necessary to arrange a supporter, that is, a spacer, in order to overcome the dynamic stresses and maintain a gap between the two glass plates.
The spacer itself has to retain a large compression strength to effectively withstand the pressure applied by atmospheric pressure and has to be firmly fixed to a designated position. As a spacer forming method in the related art, there is a method of partially applying a glass glue liquid to the glass plate and distributing the spacers to fix the spacers to positions where the glass glue liquid has been applied. However, omission or errors in arrangements of the spacers frequently occur in the method, which may generate errors in products.
In a case of a large area vacuum glass panel, a method of disposing a lattice-shaped spacer between two glass plates and welding the spacer and the glass plates by using an ultrasonic wave, a laser beam or the like in an electric furnace of a vacuum atmosphere is disclosed. However, the method requires expensive equipment and has a complicated manufacturing process.
Meanwhile, stress applied to the glass plate significantly varies depending on an arrangement type and a gap of the spacers. When the spacer does not uniformly support an external pressure over an entire vacuum glass panel, a crack is generated by stresses from the glass plate itself according to a pressure inclination phenomenon. Further, a tensile stress is generated near the spacer in the external surfaces of the glass plate, and when the tensile stress exceeds a maximum allowable tensile stress, self-destruction occurs.
Accordingly, researches on an optimal arrangement type, arrangement gap and the like of the spacer, which can improve a mechanical strength of the vacuum glass panel or maintain the mechanical strength of the vacuum glass panel with the minimum number of spacers by considering a distribution of the stresses applied to the glass plate are required.
In addition, in the general vacuum glass panel, edges of two glass plates are integrally welded by a sealing material, an internal space is evacuated through an exhaust hole formed in one glass plate, and then the exhaust hole is sealed by a cap member, so that the vacuum glass panel remains in a vacuum state.
The sealing material is formed of a general glass frit, and is disposed between two glass plates and then heated at a temperature equal to or higher than approximately 400° C. in the atmosphere. Then, the sealing material is melted and integrally welded with the two glass plates. However, such a high temperature sealing method may create deformation or discoloration of the glass plate. For example, in a case of a low emissivity glass plate, a metal coating film is oxidized and discolored, and as a result, a radiant heat blocking function may be lost.
In order to compensate for the high temperature sealing method, a low temperature sealing method of melting the sealing material at a temperature of approximately 200° C. by using a low melting point sealing material including indium has been proposed. However, in this case, a manufacturing cost of the vacuum glass panel is increased since the sealing material is expensive, and a degassing phenomenon is generated from the sealing material after being evacuated and thus a vacuum degree of the vacuum glass panel is reduced, thereby deteriorating the insulation performance.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.